This invention relates to a method of making a glass structure, and particularly to such a method in which cylindrical spacers are utilized to assemble a structure which includes a plurality of uniformly spaced glass plates.
Display devices have been proposed which include a plurality of spaced parallel glass plates which are disposed between a back surface and a front viewing surface. The back surface includes a cathode area and the front surface includes a phosphor viewing screen. The glass plates are maintained in parallel relation through a bond to a common surface. The common surface may be glass surface, e.g., the front or back surface. The spaces between the glass plates may include structure for multiplying and/or modulating electrons emitted from the cathode. However, in any case, it is particularly desirable that the spacing between adjacent plates be substantially uniform since this spacing can be employed to fix at least one dimension of each particular display element, e.g., image line height or image line width. Thus, the element uniformity of the display device is strongly dependent on the spacing between adjacent glass plates.
Display devices of this type would be useful as a relatively large flat image display device. For example, such a device may have viewing dimensions on the order of 30" .times. 40" (75 .times. 100 cm) with a thickness of about 1" (2.5 cm). In such a structure, for good resolution, it may be desirable that each of the glass plates be rectangularly shaped and about 40" .times. 1" .times. 0.020" (100 .times. 2.5 .times. 0.05 cm). In one embodiment, a desirable spacing between adjacent glass plates would be about 60 mils (0.15 cm).
Conventional techniques are not capable of constructing such a glass structure without the use of expensive bulky equipment, i.e., fixtures. In addition, in most of these techniques, additional non-uniformities are introduced into the spacing between the plates due to the use of spacers which are in fixed position. That is, dimensional tolerance in fixture parts results in unacceptable errors in spacing. Also, these techniques often cause sagging during assembly since the use of heat is typical during bonding. Further, these techniques often result in internal stresses within the glass structure which subsequently cause cracking or breaking. These stresses are typically caused by expansion differences in the fixture which occur during heating and cooling. Thus, it would be desirable to develop a simple method of making a glass structure which permits the construction of a plurality of uniformly spaced glass plates.